I agree to an extent. However, I'll just point out that as a wall it isn't going to ever be a very good one. It is trivial to breach. Especially by a group of players. So I'm not sure I would refer to doing it as "cheating". It is a poor man's wall at best.
Should be possible with specific trees, like birch and other small ones. Large trees should not be able to be placed directly next to each other. In fact, get rid of the entire grid system with trees, so they don't look so uniform in the exact center of the grid when planting. Then make larger trees kill of other trees planted too closely, and people would have to use player skill in order to plant trees effectively.
Tree walls are easy to deal with during JH on the enemy Realm Claim. You can simply cut them down. However, oak trees are immune to the siege weapons. And it takes time anyway to do the above mentioned. I've been playing the game since middle school and now I can write a game review for https://writemyessaysonline.com more than 500 words - essay from scratch.